The invention relates to an improved variable laser power delivery apparatus and a method for delivery of a variable laser power. The invention also relates to an improved attenuator and an improved polarizer.
Laser beams are widely used for a variety of purposes such as drilling, microwelding and the like. It is desirable to be able to vary the power of the laser so that same laser can provide laser beam of variable power. UV beams can be particularly difficult to handle due to the destructive nature of the beams. Prior efforts have been made in this regard. See U.S. Pat. No. 5,103,454. Such prior art devices are cumbersome and may result in the release of unshielded UV radiation into the work place.
According to the invention, a variable laser power delivery apparatus is provided. The apparatus includes a generator for delivering a preselected polarized wavelength beam preferably an ultraviolet (UV) beam along an optical beam path. A dichroic mirror, desirably two (2) or more, preferably four (4) dichroic mirrors, for transmitting the preselected UV wavelength laser beam at P-polarization and for highly reflecting the preselected UV wavelength laser beam at S-polarization are located along the preselected optical beam path delivered from the laser beam generator. A beam polarization rotator is mounted along the optical beam path provided The beam polarization rotator is located between the laser beam generator and the dichroic mirror along the optical beam path. A beam output is provided by directing the beam transmitted or reflected by the dichroic mirror to a preselected location as the output of the device. Alternatively when two beam outputs are desired, both the reflected and the transmitted beams can be used as laser beam outputs. Preferably the reflected beam is used as the output. Desirably, particularly when a UV beam is used, the unused UV beam from the dichroic mirror is directed to a UV beam block or shield to prevent release of UV radiation into the workplace. Preferably the polarization rotator is a waveplate, most desirably a half waveplate mounted to rotate the polarization of the polarized laser beam. The half waveplate rotates between 0 and 45 degree from its xe2x80x9cCxe2x80x9d axis so that the polarization of the laser beam can be rotated from 0 to 90 degree prior to the polarized laser beam incidenting on the dichroic mirror.
In operation a laser generator delivers a preselected wavelength polarized laser beam along an optical beam path. The beam is passed across the polarization rotator which is rotatably mounted along the optical beam path. Desirably the beam polarization rotator is a half waveplate which is rotatably mounted to rotate from 0 to 45 from its xe2x80x9cCxe2x80x9d axisxe2x80x9d. The polarized UV beam passes through the polarization rotator where the polarization is rotated from 0 to 90. The resulting beam is directed to the dichroic mirror or mirrors where the P-polarized component of the UV beam is transmitted and the S-polarized component of the UV beam is reflected. Depending on the amount of power desired, the polarization rotator is rotated between 0 and 45 degree to vary the amount of transmitted power from 0% to close to 100%.
In another aspect of the invention, multiple dichroic, preferably four (4) mirrors, are provided in optical communication with the beam propagating from the polarization rotator. The beam from the polarization rotator is directed to a first dichroic mirror which is highly reflective for the preselected wave length beam at S-polarization and highly transmissive for the beam at P-polarization. The reflected beam is directed to a second dichroic mirror which is also highly reflective for S-polarization and highly transmissive for P-polarization. The reflected beam is then either used as the output of the laser or directed to additional dichroic mirrors where the S-component is reflected and the P-component is transmitted. Desirably, third and fourth dichroic mirrors are used with the reflected beam of the second dichroic mirror in optical communication with the third mirror and the reflected beam of the third mirror in optical communication with the fourth mirror.
In another aspect of the invention a laser beam polarizer is provided. The polarizer includes two (2) or more dichroic mirrors which are highly reflective at S-polarization and highly transmissive at P-polarization. Each mirror in the polarizer is in optical communication with the next mirror in the series.
For un-polarized laser beam or partially polarized beam, the beam to be linearly polarized incidents on a first dichroic mirror where the S-component of the beam is reflected. The reflected beam is then directed to a second dichroic mirror where the S-component is again reflected and the P-component is transmitted. Optionally, a third and fourth dichroic mirror can be used where the process is repeated. The resulting beam has a high degree of linear polarization. If the S-component is smaller than the P-component when the beam incidents on the first mirror, a polarization rotator can be used to maximize the S-component.
It is an objective to provide laser power attenuator for continousely varing the laser power output with high polarization contrast ratio and broad power tuning range.
It is an objective to provide laser power attenuator, particularly for ultra violet lasers for continuously varing the laser power output with high polarization contrast ratio and broad power tuning range.
It is also an objective to provide laser power polarizer with high polarization contrast ratio and low loss.
Other and further objects will be come apparent from the specification, drawings and claims.
The preferred embodiment of the present invention is illustrated in the drawings description and the examples. However it should be expressly understood that the present invention should not be limited soley to the illustrative embodiment.